A known hybrid vehicle has an engine, a motor/generator (MG) used for driving, starting of the engine and power generation, and a clutch that is disposed between the engine and the motor/generator. When such a hybrid vehicle coasts, a fuel supply to the engine is stopped and the clutch is disengaged so the engine is isolated from a drive transmission and the motor/generator. With this operation, there is no loss of electrical energy regeneration due to engine friction during a deceleration regenerative power generation by the motor/generator, and a regenerative power amount is secured fully and efficiently. In such a hybrid vehicle, for instance, when the hybrid vehicle coasts down a long hill with an accelerator pedal released by a driver, the MG is used as the generator, and a frequency or the number of occurrences of recovering electricity by performing the regenerative power generation increases.
In this situation, it is conceivable that a situation will often occur in which a battery that stores the regenerative power or electricity becomes fully charged. That is, it is conceivable that a case will often occur where a state of charge (SOC) of the battery exceeds a specified value, and regeneration becomes impossible. Thus, in the case where the SOC exceeds the specified value, in order to prevent an overcharge of the battery, a regenerative braking by the MG is controlled or restrained (or suppressed). For this case where the regenerative braking is restrained even though the driver releases the accelerator pedal, there are systems such as those taught in Japanese Patent Provisional Publication Nos. 2004-162534 and 2006-306328 in which a clutch arranged between the engine and the motor is engaged, and the deceleration is performed by the engine friction. In addition, a system with a stepped transmission in such hybrid vehicle provided with two clutches has also been disclosed in, for example, Japanese Patent Provisional Publication No. 2005-221073.